1. Field of the Invention
The invention concerns a shielded electrical connector in the form of an insulative block provided with compartments adapted to receive electrical contact members housed in a shielded housing comprising two metal half-shells having complementary coupling means, the casing being intended to be overmolded with an insulative material.
2. Description of the Prior Art
Electrical connectors of the above design are described and shown in the documents FR-2 654 558 and EP-A-0 180 594 which provide a full treatment of the design of this equipment and the problems raised by its manufacture. These problems include industrial constraints but also and more importantly problems relating to the electrical continuity of the shielding and to the mechanical strength of the housing when subject to the injection molding pressure when the insulative material is overmolded onto it.
According to the document FR-2 654 558, the mechanical strength problem is apparently solved by a housing in the form of two stamped metal half-shells a "lower" one of which is provided with a lateral skirt nesting in the "upper" half-shell, the rear part of the peripheral wall of which is provided with openings into which clip locking lugs of complementary shape provided on the rear surface of the skirt of the opposite half-shell.
The two half-shells have at the rear a semi-cylindrical part for the electrical conductors to pass through surrounded in the assembled position by a crimping ferrule. Here mechanical strength and good electrical continuity to achieve the required shielding against interference is provided by stiffening ribs pressed into each half-shell and by the partial interengagement of said shells which incorporate a ledge against which the edge of the skirt on the opposite half-shell bears.
The shielded housing is joined t the standardized rear housing comprising the insulative block by indenting the free edges at the front of the half-shells. Claw-like folded lugs obtained by cutting/stamping and then work hardening are arranged at regular intervals along the entire length of these free edges and, when the two housings are coupled together, cooperate with respective notches provided in the flange of the rear housing.
Despite this design, there is a high risk of the shells of the shielded housing being deformed by the injection molding pressure during overmolding of the insulative material with consequent transmission of forces to the parts of the insulative block (leading to breakdown and short-circuiting) if no leakage path is provided to act as a pressure limiter and to regulate temporary pressure rises during molding.
Furthermore, although the shells have some degree of symmetry, they cannot be arbitrarily substituted for each other because they are of complementary design (male and female) and necessarily require differently conformed cutting tools, in particular punches.
According to the document EP-A-0 180 594 the problem of the mechanical strength of the shielded housing during overmolding of the insulative material is solved by pressure relief vents in the form of flaps obtained by cutting the back of the shells in a figure that is not closed. If the molding pressure is within permissible limits, the flaps remain in the same plane as the back (to oppose the intrusion of plastics material into the housing). However, if the pressure crosses a critical threshold, the flaps are pushed back towards the interior of the housing by pivotting about the uncut portion to allow a quantity of the material to be extruded into the interior of said housing. This design enables a pressure regulation effect but does not, however, authorize strict control of the mass of material flowing into the interior of the housing with the risk, in the case of high pressure, of affecting the electrical connections, in particular the insulative sheaths of the electrical conductors connected to the connecting members, or of modifying the position of the connecting terminals.
An object of the invention is to alleviate the drawbacks encountered with the prior art equipment.